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Grand Island Resources, LLC Page 2 <br />Idaho Tunnel Portal – Slope Stability Analysis <br />Applied GeoLogic LLC 5/7/2020 <br /> <br />Photograph 1 – Idaho Tunnel Portal prior to Rehabilitation <br />The timbered tunnel entrance and area around the opening were excavated in November 2019 in order <br />to stabilize the tunnel portal. This effort involved excavating approximately 25 feet into the hillside, <br />installing soil anchors, and applying a layer of shotcrete of variable thickness (Photograph 2). This work <br />was performed by Harrison Western Construction Corporation, a licensed contractor. <br />The tunnel portal is being enlarged to a nominal 10-ft. x 10-ft. opening in order to replace the existing <br />ground support which is failing and remove the loosened rock surrounding the present opening. The <br />enlarged tunnel opening is supported by steel sets installed at 4-ft center-to-center spacing with full <br />lagging on the back and ribs. The steel sets consist of W6x20 wide-flange I-beams and support posts. The <br />lagging consists of 3-in. x 8-in. Douglas Fir planks. Grouted threadbar spillings were installed at 12-inch <br />spacing above the tunnel opening prior to excavation. <br />In December 2019 a roof collapse occurred a short distance into the tunnel during initial rehabilitation <br />efforts by Harrison Western. The roof failure occurred in an 11-12 ft section of unsupported ground as <br />the tunnel opening was being enlarged through a section of mixed soil and decomposed gneiss. The <br />collapse completely blocked the mine opening, crushed the pipe carrying the flow of mine water, and <br />daylighted in the slope below County Road 128 (Caribou Road), leaving a large remnant void above the <br />tunnel opening which estimated to be approximately 65 cubic yards. <br />